Ignition coil

ABSTRACT

An ignition coil comprises a transformer having a small number of primary windings and a large number of secondary windings. The secondary windings are connectable to at least two spark gaps, each being connected by way of a reed-type relay which can be opened or closed, typically, by a solenoid in response to a required sequence.

United States Patent 1 1 Johnson et a1.

' Apr. 27, 1973 IGNITION COIL Inventors: Frederick Stanley Johnson, Stoney Hill; Kenneth Longstaff, Alcester, both of England British Leyland UK Limited, London, England Filed: Apr. 29, 1974 Appl. No.: 464,945

Assignee:

Foreign Application Priority Data United Kingdom 20105/73 US. Cl 3l7/157.6; 123/148 D Int. Cl. F02I 7/00 Field of Search ..3l7/l57.6; 123/148 D,

References Cited UNITED STATES PATENTS 4/1920 Bohli 123/148 ND see [ 1 Oct. 21, 1975 2,782,247 2/1957 Bales 123/148 D 3,638,630 2/1972 Hetzler et a1. 123/148 D 3,807,378 4/1974 Wernet, Jr 123/148 F Primary ExaminerL. T. Hix Attorney, Agent, or FirmBrisebois & Kruger [5 7 ABSTRACT 4 Claims, 4 Drawing Figures US. Patent Oct. 21, 1975 Sheet1of3 3,914,665

US. Patent Oct. 21, 1975 Sheet 2 of3 3,914,665

US. Patent Oct.21, 1975 Sheet30f3 3,914,665

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IGNITION COIL This invention relates to an ignition coil. Such a coil is used in a spark ignition internal combustion engine to produce a high voltage pulse for supply to a sparking plug. In effect the coil is a step-up transformer providing from a secondary coil a high voltage pulse in response to a low voltage fed to a primary coil.

According to the present invention an ignition coil comprises a transformer having a relatively small number of primary windings and a relatively large number of secondary windings and at least two reed-type relays each comprising a pair of contacts adapted to be closed or opened by means of a magnetic field; means adapted to generate a magnetic field for opening or closing each relay; one contact of each pair of the relay being adapted for connection to the secondary winding; the other contact of each pair being adapted for direct, or indirect, connection to a spark gap.

An ignition coil embodying the invention will now be described with reference to the accompanying drawing of which:

FIG. 1 is a sectioned elevation;

FIG. 2 is a plan view of the coil when viewed in'the direction of arrow II in FIG. 1;

FIGS. 3 and 4 are circuit diagrams of two embodiments of means for controlling the relays described in connection with FIGS. 1 and 2.

FIGS. 1 and 2 A primary coil 11 of relatively few turns and a secondary coil 12 having relatively many turns are disposed in an oil filled casing 13. The coils 11, 12 are electrically isolated from one another and disposed around a central core 14. Both coils 11, 12 and core 14 are mounted on an insulating pedestal 15. The upper ends of the coils 11, 12 are located by an insulator 16 on which is mounted a magnetic screening component 17. The secondary coil is electrically connected by a ring connector to one contact of each of four reed relays 18, 19, 20 and 21. Each relay comprises a housing 23 containing a pair of reed relay contacts. In each housing the upper reed relay. contact projects outside the housing 23 and is coupled to a spark plug lead connector 24. Each housing 23 comprises an evacuated glass tube and is surrounded by an annular solenoid 25 which, on the passage of a current, generates a magnetic field which serves to close the relay contacts of the housing. On the current ceasing the magnetic field collapses so allowing the contacts to spring apart to an open circuit disposition. The upper part of casing 13 has mounted on it two terminals 26, 27 and a socket 28. Terminal 26 is for linking the primary coil 11 to a source of low voltage pulses. Terminal 27 is for linking annular solenoids 25 to a source of power.

Socket 28 is a four pin socket. Each pin is connected to one of the annular solenoids 25 to enable that solenoid to be energised by a pulse fed to terminal 27.

In use when mounted in an engine ignition system each of relays 18 to 21 in turn are closed by completing the circuit of the appropriate annular solenoid 18 by way of socket 28 and terminal 27.. The resulting mag netic field causes the appropriate relay to close. Thereafter an ignition pulse is fed to terminal 26 and so primary coil 11. The transformer coupling between primary coil 11 and secondary coil 12 results in a high voltage pulse being fed to ring connector 10. As a consequence whichever relay is being held closed causes the-high voltage pulse to be fed to the connector 24 and so to an engine spark plug to cause an ignition spark.

After the high voltage surge has been passed the energised solenoid is de-energised to open the corresponding reed relay contacts. The cycle is then repeated with the next reed relay in the sequence. The reed relays described make use of an evacuated casing. If preferred an oil filled casing can be used to quench incipient sparking.

Two systems will now be described by way of example for energising in sequence solenoids of the type described in connection with FIGS. 1 and 2.

FIG. 3 shows an ignition system for a four cylinder internal combustion engine. Reed relays 38 to 41 correspond to relays 18 to 21 in FIGS. 1 and 2. Each relay 38 to 41 surrounded by, respectively, solenoids 42 to 45. Relays 38 to 41 include, respectively, a first contact 46 to 49 and a second contact 50 to 53. Each of the first contacts 46 to 49-is connected to a spark plug of known type. Second contacts 50 to 53 are connected by a common line to a secondary coil in ignition coil 54 as previously described in connection with FIGS. 1 and 2. Primary coil of ignition coil 54 receives pulses of appropriate amplitude from amplifier 55. The frequency of these pulses is regulated by input fed along line 56 from a computer module 57. This module is also used to energise in sequence solenoids 42 to 45. Timing of the module outputs is governed by signals fed to inputs 58 to 59.

Engine crankshaft 60 has mounted on it a mask 61. The mask includes a gap which serves to allow light from a source 62 to pass once in every revolution of the shaft to a photo-electric cell 63. The subsequent sequencing signal generated by the cell 63 is fed to input 58 of module 57.

Engine camshaft 64 has mounted on it a mask 65. This serves to periodically isolate a light source 66 from photo-electric cells 67. The subsequent reed drive signals generated during each revolution of camshaft 64 by photo-electric cells 67 are fed to input 59 of the module 57. The sequencing signal fed to input 58 of the module provides an angular datum to which the reed drive signals fed to input 59 can be related for the purpose of calibrating the ignition system.

Module 57 feeds outputs to lines 68 to 71 which are connected, respectively, to solenoids 42 to 45. The other side of the solenoids are grounded to a common line 72.

In operation, with the engine running, signals are generated by photo cell 63, 67 as previously described and fed to inputs 58, 59 of module 57. As a result, for every engine revolution, an output signal is fed to line 56 which is amplified by amplifier 55 and passed through primary coil of ignition coil 54. The consequent high voltage pulse is then fed to second contacts 50 to 53 of relays 38 to 41. For every engine revolution also one of relays 38 to 41 is energised by a pulse fed to the appropriate solenoid along one line 68 to 71. On energisation the corresponding relay is closed so enabling high tension voltage to be fed to the spark plug associated with the relay.

FIG. 4 shows an alternative ignition system for a four cylinder internal combustion engine. Reed relays 75 to 78 correspond to relays 18 to 21 in FIGS. 1 and 2. Each relay is surrounded by, respectively, solenoids 79 to 82. Relays 75 to 78 include, respectively, a first contact 83 to 86 and a second contact 87 to 90. Each of the first contacts is connected to a spark plug (not shown)-of known type. Second contacts 87 to 90 are connected by a common line 91 to secondary coil of ignition coil 92 as previously described in connection with FIGS. 1 and 2. Primary coil of ignition coil 92 receives voltage pulses from contact breaker contacts 93 along line 94. The contacts 93 are periodically opened and closed by action of rotating cam 95 on cam follower 96.

Breaker contacts feed by way of line 97 a voltage wave form, of the type indicated at A, as input to pulse shaper module 98. This provides a substantially square wave, of the type indicated at B, to input 99 of logic cir- A Logic circuit module 100 provides, on outputs 106 to v 109 pulses in the appropriate sequence toenergise solenoids 79 to 82.

In operation, with the engine running, signals are generated, by photo cell 105 and contacts 93, as'previously described.

As a result, for every engine revolution, an output signal is fed to ignition coil'92 along line 94. A resulting high voltage pulse is fed to second contacts 87 to 90 of relay 75 to 78. For every engine revolution also one of relays 75 to 78 is energised by a pulse fed to the appropriate solenoid along one of lines 106 to 109. On energisation the corresponding relay is closed so enabling high tension voltage to be fed to the spark plug associated with the relay.

We claim:

1. An ignition coil comprising a transformer having a relatively small number of primary windings and a relatively large number of secondary windings and at least two reed-type relays each comprising a pair of contacts adapted to be closed or opened by means of a magnetic field; means adapted to provide a magnetic field for opening or closing each relay; one contact of each pair of the relay being adapted for connection to the secondary winding; the other contact of each pair being adapted for connection to a spark plug.

2. An ignition coil as claimed in claim 1 wherein the means adapted to generate a magnetic field for opening or closing each relay comprises a solenoid.

3. An ignition coil as claimed in claim 2 wherein the transfomer, the relays and the means adapted to generate a magnetic field are enclosed in a common housing.

4. An ignition coil as claimed in claim 2 connected to a computer or logic module, said module being adapted to be connected to an internal combustion engine and to receive from said engine, as input, signals related to engine speed, and to consequently provide,

as output:

a. signals which cause each generating means to generate a magnetic field to actuate a reed relay; and

b. a signal which causes the passage of a current through the primary winding of said ignition coil. 

1. An ignition coil comprising a transformer having a relatively small number of primary windings and a relatively large number of secondary windings and at least two reed-type relays each comprising a pair of contacts adapted to be closed or opened by means of a magnetic field; means adapted to provide a magnetic field for opening or closing each relay; one contact of each pair of the relay being adapted for connection to the secondary winding; the other contact of each pair being adapted for connection to a spark plug.
 2. An ignition coil as claimed in claim 1 wherein the means adapted to generate a magnetic field for opening or closing each relay comprises a solenoid.
 3. An ignition coil as claimed in claim 2 wherein the transfomer, the relays and the means adapted to generate a magnetic field are enclosed in a common housing.
 4. An ignition coil as claimed in claim 2 connected to a computer or logic module, said module being adapted to be connected to an internal combustion engine and to receive from said engine, as input, signals related to engine speed, and to consequently provide, as output: a. signals which cause each generating means to generate a magnetic field to actuate a reed relay; and b. a signal which causes the passage of a current through the primary winding of said ignition coil. 